PRESIDENT'S ADDRESS. Jxiii. 



of Purbeck fault and Chaldon fault commence east of the Isle of 

 Wight and end at Wey mouth Bay. The curving dip of the strata 

 at Ballard Cliff, near Svvanage, becomes vertical under the fault, 

 which cuts across the edges of the vertical strata beneath. The 

 great Ridgeway fault and fold show evidence of displacement, for 

 several horizons of the chalk come into contact with the Purbeck 

 rocks. At Sutton Poyntz the cretaceous beds are interrupted by 

 a curving fracture, which cuts through the Greensand, and the Lower 

 and Middle Chalk. Throughout the length of this disturbance 

 the Upper Cretaceous rocks dip at a steep angle of from 60 to 

 80. In the well-known Eidgeway cutting the Oxford clay is 

 seen in an unexpected position. The Portland, Purbeck, and 

 Wealden beds occur in their proper sequence, but between 

 the Wealden and Chalk rises a ridge or dyke of clay 

 containing numerous Oxford Clay fossils and some blocks 

 of Cornbrash. The dyke is 30 or 40 yards wide. The 

 explanation hitherto given of the Oxford Clay at Ridgeway 

 depended on the existence of two systems of disturbance. It 

 was necessary to suppose that a fault with a downthrow north 

 belonging to the later system of disturbances had been superimposed 

 upon a fault with a downthrow south and of pre-cretaceous age, and 

 that the earlier fault had not only been of enormous magnitude, but 

 that it had followed an almost impossibly crooked course. The 

 alternative explanation given is that the faults are of post-cretaceous 

 age, but are over-thrusts, not normal displacements. Then the 

 Oxford Clay has not been faulted against Wealden, but thrust 

 southwards over it, and similarly the Forest Marble, <fec., of 

 Bincombe has been thrust southwards over the Kimmeridge Clay. 



There is a paragraph in Hutchins' " History of Dorset " under 

 the head of Swyre, saying that there is a quarry in which has been 

 found the " Lapis Judaicus, Jew-stone, a stone exactly resembling 

 half a peasecod, of a faint green colour, the place where the 

 fracture may have been is smooth as if smoothed by art." It is 

 nothing more or less than a fossil. Instead, therefore, of its being 

 a Jew-stone, it is a Jaw-stone, and can be identified as the 



